Torsions impact energy absorbing device

ABSTRACT

An impact energy absorbing device includes a pair of tubular members arranged for telescopic movement relative one another upon application of impact force thereto, a third tubular member attached to one of the pair of tubular members by annular elastomeric bushings press-fitted in radial compression between the walls of the respective tubular members, and a rotary motion producing mechanism in connection between the third tubular member and the other of the pair of tubular members to convert axial telescopic movement of the pair of tubular members into rotary movement of the third tubular member causing torsional energy storing as well as energy dissipating wind-up of the elastomeric bushings. Relief of the impact force permits the energy stored in the wound-up elastomeric bushings to restore the tubular members to their pre-impact relative positions in readiness for subsequent impacting.

United States Patent [1 1 Ristau I 1 Feb. 27, 1973 TORSllONS IMPACTENERGY ABSORBING DEVICE [75] Inventor: Theodore IF. Ristau, Saginaw,Mich.

[58] Field of Search ..1 14/219; 188/129; 267/140, 267/154; 293/70, 85,89

[56] References Cited UNITED STATES PATENTS 3,390,546 7/1968 Jewell..267/154 3,369,634 2/1968 Mazelsky ..293/70 X 3,635,314 1/1972 Mazelsky..293/70 X Primary Examiner-Drayton E. Hoffman AssistantExaminerl-loward Beltran Attorney-W. E. Finken et al.

[57] ABSTRACT An impact energy absorbing device includes a pair oftubular members arranged for telescopic movement relative one anotherupon application of impact force thereto, a third tubular memberattached to one of the pair of tubular members by annular elastomericbushings press-fitted in radial compression between the walls of therespective tubular members, and a rotary motion producing mechanism inconnection between the third tubular member and the other of the pair oftubular members to convert axial telescopic movement of the pair oftubular members into rotary movement of the third tubular member causingtorsional energy storing as well as energy dissipating wind-up of theelastomeric bushings. Relief of the impact force permits the energystored in the wound-up elastomeric bushings to restore the tubularmembers to their pre-impact relative positions in readiness forsubsequent impacting.

4 Claims, 5 Drawing Figures PATENTEB FEB 2 71973 SHEET 10F 2 INV EN TOR.fie dare f/lfsiau ATTORNE Y PATENTEB FEB2 7 I975 SHEET 2 [IF 2 I N VENTOR. fieodore Zfiz'siaa AT TOR N E Y TORSIONS IMPACT ENERGY ABSORBINGDEVICE The invention relates to an improved energy absorbing device andmore particularly to an impact energy absorbing device which isself-restored to the operative condition subsequent to impactabsorption.

It is advantageous in automotive vehicle collapsible steering columnassemblies and bumper mounts, and in diverse other applications, toprovide a mechanism capable of absorbing kinetic energy. Furthermore, itis desirable, at least in the event of impacts up to a predeterminedlevel, to provide an energy absorbing device which, subsequent toimpacting, restores itself to its pre-impact condition so that it mayrepeat its energy-absorbing function upon subsequent impacts.

The present invention features an impact energy absorbing device whichis self-restored to the pre-impact condition in readiness for subsequentimpacts. The invention includes a pair of tubular members which arerotationally stationary relative one another and are arranged fortelescopic movement relative one another upon application of impactforce thereto. A third tubular member is attached to one of the pair oftubular members by press-fitting annular elastomeric bushings betweenthe walls thereof. A rotary motion producing mechanism is provided inconnection between the third tubular member and the other of the pair oftubular members to convert axial telescopic movement of the pair oftubular members into rotary movement of the third tubular member. Forcedrotation of the third tubular member causes energy storing elasticdeformation or winding up of the annular elastomeric bushings andsimultaneous kinetic energy dissipation by virtue of internal viscousflow of the viscoelastic bushing material. When the impact force isrelieved, the energy stored in the wound-up elastomeric bushings rotatesthe third tubular member to its original rotary position and actsthrough the rotary motion producing mechanism connecting the thirdtubular member and the other of the pair of members to impart retrogradetelescopic movement to the pair of tubular members, thus restoring theenergy absorbing device to the pre-impact condition in readiness for thenext impact.

In one embodiment of the invention hardened balls seated in helicalgrooves formed on both the third tubular member and the other of thepair of tubular members function to impart rotary movement to the thirdtubular member when the pair of tubular members are telescoped by theimpact force. In another embodiment of the invention a cam roller andramp arrangement acts between the third member and the other of the pairof members to produce the rotary movement of the third tubular member.An axial spline may be provided in the energy absorbing device toprevent relative rotary motion between the pair of telescoping tubes, oralternately the pair of tubular members may be fixedly attached torelative rotationally stationary bodies to which the impact force isapplied.

These and other features of the invention will be readily apparent fromthe following specification and from the drawings in which:

FIG. 1 is a perspective view having parts broken away and in sectionshowing a pair of energy absorbing devices embodying the invention andarranged in connection between a vehicle frame member and a bumperassembly;

FIG. 2 is an enlarged view of a portion of FIG. 1;

FIG. 3 is a longitudinal section view of a second embodiment of theinvention;

FIG. 4 is an elevational view taken along the plane indicated by lines4-4 of FIG. 3; and

FIG. 5 is a cross-section view taken along the plane indicated by lines5-5 of FIG. 3.

Referring to FIG. 1, the invention is shown arranged for use within anenergy absorbing bumper assembly, a use for which the invention isparticularly wellsuited, although by no means limited. A pair of energyabsorbing devices, generally indicated at 10 and 12, are constructedaccording to the invention and mount a bumper or impact bar 16 to avehicle frame member 14. The energy absorbers 10 and 12 are laterallyspaced either side of the longitudinal centerline of the vehicle,providing dual bumper mounts and holding the bumper l6 rotationallystationary relative the frame member 14. The energy absorber 10, thefollowing description of which will be understood as applyingidentically to energy absorber 12, includes a tubular member 18 suitablyconnected to frame member 14 as by welding, a tubular member 20connected to the bumper 16 as via a rigidly attached flange 21 bolted tothe bumper, and a tubular member 22. The tubular members are arrangedgenerally concentrically with tube 20 extending inside tubular member 22and tubular member 22 in turn extending inside tubular member 18.Annular elastomeric bushings 24, 26, 28 and 30 have an interference fitwithin the annular space between tubular members 18 and 22, i.e., theundeformed thickness of the bushings is predeterminedly larger than theannular space. This interference fit may be varied for best results byexperimentation for the purposes set forth hereinafter. The resultingradial compression of the elastomeric bushings causes the outerperipheral and inner peripheral surfaces of the bushings to respectivelyfrictionally engage the tubular member 18 and the tubular member 22 tosuch an extentthat the tubular members will not move substantiallyaxially relative one another and can move rotationally relative oneanother only by energy absorbing deformation of the elastomericbushings.

Referring to the enlarged view of FIG. 2, a plurality ofcircumferentially spaced helical grooves 32 are formed on the innerperipheral surface of tubular member 22, and helical grooves 34corresponding to grooves 32 and of the same hand are formed on the outerperipheral surface of tubular member 20. The grooves 32 and 34 are shownto be of equal helix lead and of equal circumferential spacing, althoughthe leads of the respective sets of grooves may be varied. A pluralityof balls 36 are press-fitted between the tubular members 20 and 22 andride in the grooves 34 and 32 formed respectively thereon. Each of theballs 36 are captured in an aperture of a ball retaining sleeve 38having a wall thickness less than the diameter of balls 36. It is notedthat it is advantageous to arrange the helical grooves and balls in atleast two axially spaced rows as shown in FIG. 2 to insure smoothtelescopic movement of tubular member 20 when side impact loads tend tobend the energy absorber 10.

The helical grooves 32 and 34 may be simply and economically formed onthe tubular members 20 and 22 in the following manner. The balls 36 arepressfitted in the apertures of ball retaining sleeve 38. The ends oftubular members 20 and 22 are chamfered to facilitate the starting ofballs 36 into the annulus between the tubular members, the annulus beingpredeterminedly smaller than the diameter of the balls. One of thetubular members is forcibly telescoped into and rotated relative theother which is held stationary, causing the balls 36 to roll between thetubular members and brinell the helical grooves 32 and 34 respectivelythereon. The helix lead is of course determined by the relative rates oftelescopic and rotational movement of the tubular members. The tubularmembers may then be pulled axially apart and the balls 36 will ride inthe grooves causing the tubular members to rotate relative one another.It isnoted that while the pressfitting of the balls into the annulusbetween the tubes leaves a residual stress in the tubular members whichresults in some energy dissipation when the tubular members aretelescoped relative one another, this energy dissipation is preferablysmall in comparison with the magnitude of energy dissipated by wind-upof 20 the elastomeric bushings as will be described hereinafter.

The energy absorbing bumper assembly is shown in FIGS. 1 and 2 in theunimpacted condition wherein the energy absorbers and 12 hold the bumper16 in axial spaced relation from the frame member 14. In operation, whenthe bumper l6 collides with a resisting object, the energy absorbers 10and 12 are loaded in compression by the axial impact force, causing thetubular member 20 to telescope into tubular members 18 and 22. Thistelescoping movement acts on the balls 36 in helical grooves 32 and 34so that the balls in turn cause tubular member 22 to be rotated in thedirection of arrows 39 relative the rotationally fixed tubular members18 and 20. Rotation of tubular member 22 causes the annular elastomericbushings 24, 26, 28 and 30 to be wound-up or torsionally elasticallydeformed to the extent that the rotational displacement energy impartedto tubular member 22 is sufficient to overcome the natural resistance ofthe bushings to such deflection.

By proper selection of the material of the bushings, and of the initialinterference fit thereof between the tubular members, the bushings arecapable of a great deal of energy dissipation. For example, theviscoelastic behavior of natural rubber is quite sufficient forirreversible absorption of a large percentage of the rotational energyapplied to tubular member 22. The dynamic loading of the energyabsorbing device by the kinetic impact energy and the consequentdeformation of the bushings results in a large amount of viscous flow inthe body of the bushings. This viscous flow is irreversible and resultsin energy dissipation. The amount of energy not so dissipated is ofcourse retained in the bushings as elastic deformation potential energyuseful for return of the energy absorbing bumper assembly to itspre-impact position. The relative proportions of dissipated versusstored energy may be varied by selection of the elastomeric material andfurthermore is dependent on the dynamic loading encountered in aparticular impact.

Thus, when the impact force is relieved from frame member 14 and bumper16, the energy absorbing devices 10 and 12 restore the bumper 16 to itspre-impact spaced relation from frame member 14 in readiness forsubsequent impacting. The elastic potential energy stored in elastomericbushings 24, 26, 28 and 30 urges the tubular member 22 to rotate to itspre-impact rotary position wherein the elastomeric bushings areundeformed. The torque imparted to tubular member 22 by the unwinding ofthe elastomeric bushings is translated into an axial thrust by thecooperation of balls 36 with helical grooves 32 and 34 to impartretrograde telescopic movement to the tubular member 20 and thereby,with the assistance of identical action in energy absorber 12, returnthe bumper 16 to its preimpact spaced relation from frame member 14.

Referring to FIG. 3, an energy absorbing device indicated generally at50 embodies a second form of the invention. The energy absorber 50includes a tubular member 52 connected to the frame member 54 and atubular member 56 connected to a bumper 58. Tubular member 56 istelescopically movable relative to tubular member 52 and is locatedconcentrically thereto. A plurality of equally circumferentially spacedaxially extending grooves 60 are formed on the inner peripheral surfaceof tubular member 56, and an equal number of mating axially extendinggrooves 62 are formed on the outer peripheral surface of tubular member52. A plurality of balls 64 are press-fitted between tubular members 52and 56 and ride in the grooves 62 and 60 formed respectively thereon.The balls 64 are held in two axially spaced annular rows by a ballretaining sleeve 66 which captures the balls 64 in axially spacedapertures formed therein. The grooves 60 and 62 may be formed bystarting the balls 64 into the annulus between the tubular members 52and 56 and then telescoping the tubular members relative one anothercausing the balls to roll and brinell the axial grooves into the tubularmembers. During telescopic movement between tubular members 52 and 56,the balls 64 ride in grooves 60 and 62 maintaining axial alignment ofthe tubular members when subjected to side impact loads and alsopreventing relative rotation between the tubular members 52 and 56.

A third tubular member 67 is arranged concentrically with tubular member56. Annular elastomeric bushings 68, 70, 72 and 74 are press-fitted intothe annular space between tubular members 56 and 67. A pair of radiallyraised cam surfaces'76 and 78 are carried by tubular member 67 atdiametrically opposed points. A pair of cam rollers and 82 are bolted atdiametrically opposed points to a tubular member 84 which is fixedlyattached relative tubular member 52. The cam rollers 80 and 82respectively coact with the cam surfaces 76 and 78 to establish therelative rotary and axial rest positions between the respective tubularmembers as shown in FIGS. 3, 4 and 5.

When the bumper 58 is impacted against a resisting object, the energyabsorber 50 is loaded in compression by a generally axially acting forcewhich causes tubular member 56 to move telescopically relative tubularmember 52. Axial movement of tubular member '56 is permitted only byvirtue of ramp surfaces 76 and 78 respectively riding over cam rollers80 and 82 and consequently forcibly rotating tubular member 67 relativethe tubular members 52 and 56. The axial spline formed by balls 64riding in grooves 60 and 62 prevents rotation between the tubularmembers 52 and 56 and also dissipates some small amount of energy inovercoming the residual stress resulting from press-fitting balls 54between the tubular members 52 and 56. Rotation of tubular member 67causes energy storing and dissipating torsional elastic deformation orwinding up of the annular elastomeric bushings 68, 70, 72 and 74.

Relief of the impact force from the frame member 54 and bumper S8 permitretrograde axial telescoping movement between tubular members 52 and 56.As the impact force is relieved, the elastomeric bushings 68, 70, 72 and74 impart to tubular member 67 a torque which acts through theengagement of cam rollers 80 and 82 with. ramp surfaces 76 and 78 torestore tubular member 67 to its rest rotary position and simultaneouslymove tubular members 67 and 56 axially to their axial rest position.

It is noted that the energy absorbing device 10 of FIG. 1 is limited toapplications wherein the tubular members 18 and 20 may be fixed tobodies which are rotationally stationary relative one another while theenergy absorber 50 of FIG. 3 includes an integral antirotation device inthe form of an axial spline including the balls 64 and grooves 60 and 62which prevents rotary movement between tubular members 52 and 56. Thus,energy absorber 50 is not limited to applications wherein the tubularmembers 52 and 56 must be nonrotatably attached to rotationallystationary bodies.

It is apparent from the foregoing discussion that the energy absorbingcapacity of a device embodying the invention may be varied to suitparticular applications by the selection of appropriate parameters forsuch variables as the number and viscoelastic characteristics of theannular elastomeric members, the angle and length of the cam surfaces 76and 78, or the lead and length of the helix grooves 32 and 34. It isthus apparent that energy absorbing devices embodying the invention maybe adapted for use in diverse applications.

What is claimed is:

1. A self-restoring device for absorbing the kinetic energy of impactand comprising:

a pair of coaxially aligned members telescopeable relative one anotherupon application of impact force thereto;

means preventing relative rotary movement between the pair of members;

a third member aligned coaxially with the pair of members;

elastomeric means radially compressed between the third member and oneof the pair of members;

and rotary motion producing means in connection between the third memberand the other of the pair of members acting to impart rotary motion tothe third member upon telescopic relative movement between the pair ofmembers whereby the elastomeric means is torsionally deformed todissipate energy by viscous flow in the elastomeric means and to storeenergy therein to subsequently effect return of the pair of members totheir preimpact axial relation.

2. A self-restoring device for absorbing the kinetic energy of impactand comprising:

a pair of coaxially aligned members arranged for telescopic movementrelative one another upon application of impact force thereto;

means preventing relative rotary movement between the pair of members;

a third member aligned coaxially with the pair of members;

annular elastomeric means radially compressed between the third memberand one of the pair of members;

helical grooves formed on adjacent peripheral surfaces of the thirdmember and the other of the pair of members;

at least one rolling body riding in the helical grooves to impart rotarymotion to the third member upon telescopic relative movement between thepair of members whereby torque is applied to the third member causingtorsional deformation of the annular elastomeric means and consequentenergy dissipating viscous flow thereof and elastic energy storagetherein, the stored energy being effective to subsequently return thethird member to the pre-impact rotary position thereof and therebyimpart retrograde telescopic movement to the pair of members.

3. A self-restoring device for absorbing the kinetic energy of impactbetween a pair of axially spaced rotationally stationary bodiescomprising:

a first tubular member non-rotatably attached to one of the bodies;

a second tubular member non-rotatably attached to the other of thebodies, coaxially aligned with the first tubular member andtelescopeable with the first tubular member upon application ofgenerally axially directed impact force thereto;

a third tubular member interposed radially intermediate the first andsecond tubular members;

annular elastomeric means radially compressed between the first andthird tubular members;

a plurality of helical grooves formed correspondingly on adjacentperipheral surfaces of the second and third tubular members;

and a plurality of balls fitted between the second and third tubularmembers and riding in the helical grooves to impart rotary motion to thethird tubular member upon telescoping movement between the first andsecond tubular members whereby torque is applied to the third tubularmember causing energy absorbing torsional deformation of the annularelastomeric means, dissipating energy by viscous flow therein andstoring elastic energy therein effective to subsequently return thethird tubular member to the pre-impact rotary position thereof, therebyimparting retrograde telescopic relative movement to the first andsecond tubular members to restore the pair of bodies to their preimpactaxial spaced relation.

4. A self-restoring device for absorbing the kinetic energy of theimpact and comprising:

a pair of coaxially aligned members arranged to telescope relative oneanother upon application of impact force thereto;

means preventing relative rotary movement between the pair of members;

a third member aligned coaxially with the pair of members;

annular elastomeric means radially compressed in interference fitbetween the third member and one of the pair of members;

and rotary motion producing means including a cam means and a rampsurface acting between the third member and the other of the pair ofmembers to impart rotary motion to the third member when the pair ofmembers are telescoped axially together whereby impact energy isdissipated by viscous flow in the elastomeric body and elasticallystored therein to subsequently effect return of the third member to thepre-impact rotary relation and return the pair of members to theirpre-impact relative axial positions.

1. A self-restoring device for absorbing the kinetic energy of impactand comprising: a pair of coaxially aligned members telescopeablerelative one another upon application of impact force thereto; meanspreventing relative rotary movement between the pair of members; a thirdmember aligned coaxially with the pair of members; elastomeric meansradially compressed between the third member and one of the pair ofmembers; and rotary motion producing means in connection between thethird member and the other of the pair of members acting to impartrotary motion to the third member upon telescopic relative movementbetween the pair of members whereby the elastomeric means is torsionallydeformed to dissipate energy by viscous flow in the elastomeric meansand to store energy therein to subsequently effect return of the pair ofmembers to their pre-impact axial relation.
 2. A self-restoring devicefor absorbing the kinetic energy of impact and comprising: a pair ofcoaxially aligned members arranged for telescopic movement relative oneanother upon application of impact force thereto; means preventingrelative rotary movement between the pair of members; a third memberaligned coaxially with the pair of members; annular elastomeric meansradially compressed between the third member and one of the pair ofmembers; helical grooves formed on adjacent peripheral surfaces of thethird member and the other of the pair of members; at least one rollingbody riding in the helical grooves to impart rotary motion to the thirdmember upon telescopic relative movement between the pair of memberswhereby torque is applied to the third member causing torsionaldeformation of the annular elastomeric means and consequent energydissipating viscous flow thereof and elastic energy storage therein, thestored energy being effective to subsequently return the third member tothe pre-impact rotary position thereof and thereby impart retrogradetelescopic movement to the pair of members.
 3. A self-restoring devicefor absorbing the kinetic energy of impact between a pair of axiallyspaced rotationally stationary bodies comprising: a first tubular membernon-rotatably attached to one of the bodies; a second tubular membernon-rotatably attached to the other of the bodies, coaxially alignedwith the first tubular member and telescopeable with the first tubularmember upon application of generally axially directed impact forcethereto; a third tubular member interposed radially intermediate thefirst and second tubular members; annular elastomeric means radiallycompressed between the first and third tubular members; a plurality ofhelical grooves formed correspondingly on adjacent peripheral surfacesof the second and third tubular members; and a plurality of balls fittedbetween the second and third tubular members and riding in the helicalgrooves to impart rotary motion to the third tubular member upontelescoping movement between the first and second tubular memberswhereby torque is applied to the third tubular member causing energyabsorbing torsional Deformation of the annular elastomeric means,dissipating energy by viscous flow therein and storing elastic energytherein effective to subsequently return the third tubular member to thepre-impact rotary position thereof, thereby imparting retrogradetelescopic relative movement to the first and second tubular members torestore the pair of bodies to their pre-impact axial spaced relation. 4.A self-restoring device for absorbing the kinetic energy of the impactand comprising: a pair of coaxially aligned members arranged totelescope relative one another upon application of impact force thereto;means preventing relative rotary movement between the pair of members; athird member aligned coaxially with the pair of members; annularelastomeric means radially compressed in interference fit between thethird member and one of the pair of members; and rotary motion producingmeans including a cam means and a ramp surface acting between the thirdmember and the other of the pair of members to impart rotary motion tothe third member when the pair of members are telescoped axiallytogether whereby impact energy is dissipated by viscous flow in theelastomeric body and elastically stored therein to subsequently effectreturn of the third member to the pre-impact rotary relation and returnthe pair of members to their pre-impact relative axial positions.